HHIS

• General characteristics of connective tissue

  • Most abundant tissue in the body
  • Major constituent of connective tissue is the extracellular matrix (ECM)
  • All connective tissue has 3 components: Cells, Ground substance, Fibers
  • Originate from embryonic mesenchyme
• Functions of connective tissue

  • Responsible for attachment of one tissue to another (e.g., Ligaments, Tendons)
  • Transport of fluids and materials (e.g., Blood)
  • Defending the body from invading microorganisms (immune system)
  • Storage of materials (e.g., Fat)
  • Establishing a structural framework for the body (e.g., Bones)
• Cells of connective tissue


  1. Fibroblasts: Major cells of connective tissue proper, elongated, irregularly shaped cells with oval nuclei that synthesize and secrete most components of the ECM, involved in wound healing

  2. Fibrocyte (quiescent cell): Inactive form of Fibroblast, smaller and spindle-shaped

  3. Adipocytes (fat cells): Very large cells specialized for storage of triglycerides

  4. Mesenchymal Cells: Relatively unspecialised cells capable of differentiation into all supporting tissue cell types
• Mesenchyme is the embryological tissue from which all types of supporting/connective tissue are derived
• Macrophages are short-lived cells that differentiate in connective tissue from precursor cells called monocytes and function in ECM turnover, phagocytosis, antigen presentation, and secretion of various agents
• Specialized Connective Tissue


  • Adipose Tissue
  • Cartilage
  • Bones
  • Blood
• Sources of adipocytes


  1. Dietary fat packaged as chylomicrons in the intestine

  2. Triglycerides circulating as VLDLs in the liver

  3. Fatty acids formed by adipocytes locally
• Plasma cells are short-lived cells that differentiate from B lymphocytes and are specialized for the abundant secretion of specific antibodies
• White Adipose Tissue


  • Large cells containing one large lipid droplet causing the nucleus and cytoplasm to be pushed against the plasmalemma
  • Comprises up to 20% of total body weight in normal well-nourished male adults and up to 25% in females, can reach more than 50% in obesity
  • Specialized for relatively long-term energy storage
  • Can store triglycerides from dietary fats, lipids synthesized in the liver, and free fatty acids and glycerol synthesized by the adipocyte
• Leukocytes provide surveillance against bacterial invaders and stimulate tissue repair
• Brown Adipose Tissue


  • Comprises up to 5% of a newborn's body weight, smaller amounts in adults
  • Contain many small lipid droplets in cytoplasm with many mitochondria and a central nucleus
  • Rich in mitochondria and specialized for heat generation, plays a part in body temperature regulation
  • Characterized by expression of a unique uncoupling protein, UCP1, which serves to uncouple mitochondrial metabolism from ATP production to produce heat
• Wandering Cells


  • Macrophages
  • Mast cells
  • Plasma cells
  • Leukocytes
• Cartilage


  • Tough, resilient connective tissue supporting soft tissues and providing cushioned, low-friction surfaces in joints
  • Lacks vascular supplies, chondrocytes receive nutrients by diffusion from capillaries in the perichondrium
  • ECM includes collagen and abundant proteoglycans, notably aggrecan binding a large amount of water
  • Contains high concentration of GAGs and proteoglycans
• Fixed/Resident Cells


  • Mesenchymal Cells
  • Fibroblasts/Fibrocytes
  • Adipocytes
• Ground Substance


  An amorphous transparent material with the physical character of semi-solid gel that fills the space between cells and fibers in connective tissue
• Components of Ground Substance

  • Glycosaminoglycans (GAGs/Mucopolysaccharides)
  • Proteoglycans
• Glycosaminoglycans (GAGs/Mucopolysaccharides)


  Long polymers of repeating disaccharide units, usually a hexosamine and uronic acid
• Macrophages are found in connective tissue, lymphoid organs, lungs, bone marrow, pleural and peritoneal cavities. They produce cytokines, chemotactic factors, and other molecules involved in inflammation, defense, antigen processing, and presentation
• Kupffer cells in the liver have the same functions as macrophages
• Microglial cells in the central nervous system have the same functions as macrophages
• Langerhans cells in the epidermis of the skin are involved in antigen processing and presentation
• Dendritic cells in lymph nodes and spleen are involved in antigen processing and presentation
• Osteoclasts, formed from the fusion of several macrophages, are responsible for localized digestion of bone matrix
• Multinuclear giant cells, formed from several fused macrophages, are involved in the segregation and digestion of foreign bodies
• Types of Proteoglycans


  • Aggrecan-large, core protein heavily bound with chondroitin and keratan sulfate chain
  • Perlecan-key proteoglycan in all basal laminae
• Multiadhesive/Structural glycoproteins


  • Fibronectin - binding sites for collagens and certain GAGs, forms insoluble fibrillar networks throughout connective tissue
  • Laminin - with binding sites for integrins, type IV collagen, and specific proteoglycans, providing adhesion for epithelial and other cells
• Water in the ground substance of connective tissue is referred to as interstitial fluid and has an ion composition similar to that of blood plasma
• Epithelial Tissue is a tissue composed of aggregated polyhedral cells with a small amount, lining surfaces or body cavities and involved in glandular secretion
• Connective Tissue consists of several types of fixed and wandering cells with an abundant amount, supporting and protecting tissues/organs
• Nervous Tissue is composed of elongated cells with extremely fine processes in very small amounts, involved in the transmission of nerve impulses
• Apical side


  • Facing the surface; Capable of transcytosis and pinocytosis
• Basal side


  • Facing the basal membrane; Involves exocytosis
• General Characteristics of Epithelial Tissue: Variable in shape and dimensions (Columnar/ Cuboidal/ Squamous); Cells' size and morphology are dictated by their function; Shows polarity with basal and apical poles; Avascular; All epithelial tissues lie at the basement membrane
• Functions of Epithelial Tissue: Lines internal and external body surfaces, protects from abrasion and injury, absorbs materials, transports materials, secretes mucus, hormones, and proteins, facilitates gas exchange, and provides lubrication
• Basement Membrane acts as a filter, provides structural support for epithelial cells, attaches epithelia to underlying connective tissue, and consists of a thin extracellular layer of specialized proteins with two parts: hemidesmosome, Basal Lamina, and Reticular Lamina
• Types of Junctional Complexes: 1. Occluding or Tight Junctions 2. Adherent Junction 3. Desmosome or Macula Adherens 4. Hemide
• Cells of cartilage


  • Chondrocytes synthesize and maintain all ECM; may be present in the periphery of cartilage and the lacunae, making up a small percentage of the tissue’s mass, which is mainly a flexible mass of extracellular matrix (ECM)
• Chondrocytes


  Cells of cartilage that synthesize and maintain all ECM components and are located in the lacunae
• Perichondrium


  A sheath of dense connective tissue that surrounds cartilage in most places, forming an interface between the cartilage and the tissues supported by the cartilage; harbors the blood supply serving the cartilage and a small neural component
• Forms of cartilage


  • Hyaline Cartilage
  • Elastic Cartilage
  • Fibrocartilage